The invention relates, as indicated, to greenhouse construction, and more particularly to a novel greenhouse construction which is entirely subterranean except for the provision of a hinged roof which can be elevated as desired to admit natural light into the interior of the greenhouse during appropriate light conditions. By selective opening or closing of the roof, complete photoperiodic control of the greenhouse can be obtained at all times of the year thereby avoiding shading of the crop as currently is done. At the same time, substantial energy savings are realized due to the subterranean installation of the greenhouse. Critical night temperatures can be established and maintained, either by residual heat contained in the greenhouse during the opening of the roof during the day, or by providing an additional source of heat to augment such residual heat. Artificial light in the form of light fixtures mounted on the underside of the roof also function as a heat source. In addition, a solar collector can be employed with the roof structure to further supplement the heat energy necessary to maintain the desired temperature conditions within the greenhouse.
The concept of storing vegetables and other food products subterraneally is of course well known in the art. U.S. Pat. No. 795,984 discloses an early teaching of storing fruits and vegetables in caves or tunnels under ground, with a door being provided to gain access to the cave. U.S. Pat. No. 3,938,824 discloses a root cellar which can be fabricated and then buried, with only the top wall being exposed above the ground. The purpose of the cellar is similarly to permit storage of foods, and the structure disclosed in this patent is clearly incapable of sustaining a year round greenhouse operation.
U.S. Pat. Nos. 2,639,550 and 2,639,551 disclose greenhouse constructions which are entirely above ground, but which are provided with translucent curtains or sheets which are mounted for movement by rollers for movement to desired positions relative to the top of the greenhouse construction.
The use of solar heat for building structures is of course well known in the art, with U.S. Pat. No. 2,777,253 disclosing a solar system specifically adapted to a greenhouse environment. However, the solar system is substantially different than contemplated in accordance with the present invention.
The concept of providing a slidable or liftable closure member or roof for a greenhouse in order to expose the interior thereof is also known in the art, reference being made to U.S. Pat. No. 4,014,133. However, the arrangement disclosed in this patent is totally unlike the roof construction and mounting in accordance with the present invention.